Note: Descriptions are shown in the official language in which they were submitted.
CA 02802172 2013-01-10
SYSTEM AND METHOD OF MEASURING AND MONITORING
TORQUE IN A ROTORCRAFT DRIVE SYSTEM
BACKGROUND
Technical Field:
The present disclosure relates to system and method of measuring and
monitoring
torque in a rotorcraft drive system.
Description of Related Art:
Typically, the mast torque in a rotorcraft main rotor mast, such as a
helicopter main
rotor mast, can be measured by measuring the rotational phase shift, or
torsion,
between a precision gear attached to the top of the helicopter mast and an
identical
precision gear attached to the bottom of the helicopter mast. The rotational
phase
shift between these two gears, which is caused by the twisting of the
helicopter mast,
can be measured using an inductance device. However, such a system that
measures rotational phase shift is less desirable in some rotor mast
implementations.
Hence, there is a need for an improved system and method for measuring torque
in
a main rotor mast. Further, there is a need for a system and method for
measuring
torque in a tail rotor drive shaft.
SUMMARY
In one aspect, there is provided a method of optimizing an operation of a
rotorcraft,
the rotorcraft having a tail rotor drive shaft, the method comprising:
measuring an
actual usage of the tail rotor drive shaft during operation of the rotorcraft,
the actual
usage including at least a torque measurement; adjusting a life of the tail
rotor drive
shaft based upon the measuring of the actual usage.
In another aspect, there is provided a method of determining a main rotor mast
torque during operation of a rotorcraft, the method comprising: measuring a
tail rotor
drive shaft torque during operation of the rotorcraft; deriving a main rotor
mast torque
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from the measured tail rotor drive shaft torque and a total torque output of
an engine,
the engine having a main rotor mast output and a tail rotor drive shaft
output.
In a further aspect, there is provided a system configured for determining a
main
rotor mast torque during operation of a rotorcraft, the system comprising: a
tail rotor
drive shaft sensor system configured for measuring a torque in a tail rotor
drive shaft;
an engine output sensor configured for deriving a total output torque of an
engine;
and a processor in data communication with the tail rotor drive shaft sensor
system
and the engine output sensor, the processor being configured for determining
the
main rotor mast torque based upon the total output torque of the engine and
the
measured torque in the tail rotor drive shaft.
DESCRIPTION OF THE DRAWINGS
The embodiments, as well as a preferred mode of use, and further objectives
and
advantages thereof, will best be understood by reference to the following
detailed
description when read in conjunction with the accompanying drawings, wherein:
Figure 1 is a side view of a rotorcraft having a torque measuring sensor
system,
according to an example embodiment;
Figure 2 is a side schematic view of a tail rotor drive shaft torque measuring
sensor
system, according to an example embodiment;
Figure 3 is a side schematic view of a main rotor mast torque measuring
system,
according to an example embodiment;
Figure 4 is a schematic view of a method of optimizing a tail rotor drive
shaft,
according to an example embodiment; and
Figure 5 is a schematic view of a computer system, according to an example
embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
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DESCRIPTION OF THE PREFERRED EMBODIMENT
Illustrative embodiments of the system and method of the present disclosure
are
described below. In the interest of clarity, all features of an actual
implementation
may not be described in this specification. It will of course be appreciated
that in the
development of any such actual embodiment, numerous implementation-specific
decisions must be made to achieve the developer's specific goals, such as
compliance with system-related and business-related constraints, which will
vary
from one implementation to another. Moreover, it will be appreciated that such
a
development effort might be complex and time-consuming but would nevertheless
be
a routine undertaking for those of ordinary skill in the art having the
benefit of this
disclosure.
In the specification, reference may be made to the spatial relationships
between
various components and to the spatial orientation of various aspects of
components
as the devices are depicted in the attached drawings. However, as will be
recognized by those skilled in the art after a complete reading of the present
disclosure, the devices, members, apparatuses, etc. described herein may be
positioned in any desired orientation. Thus, the use of terms such as "above,"
"below," "upper," "lower," or other like terms to describe a spatial
relationship
between various components or to describe the spatial orientation of aspects
of such
components should be understood to describe a relative relationship between
the
components or a spatial orientation of aspects of such components,
respectively, as
the device described herein may be oriented in any desired direction.
Referring to Figure 1 in the drawings, a rotorcraft 101 is illustrated.
Rotorcraft 101
has a rotor system 103 with a plurality of main rotor blades 111. Rotorcraft
101
further includes a fuselage 105, landing gear 107, a tail member 109, and tail
rotor
blades 113. An engine 115 supplies torque to a main rotor mast 117 and a tail
rotor
drive shaft 119, for the rotating of main rotor blades 111 and tail rotor
blades 113,
respectively. The pitch of each main rotor blade 111 can be selectively
controlled in
order to selectively control direction, thrust, and lift of rotorcraft 101.
Further, the
pitch of tail rotor blades 113 can be selectively controlled in order to
selectively
control yaw of rotorcraft 101.
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Referring now also to Figure 2, a tail rotor drive shaft torque measuring
sensor
system 201 is illustrated in conjunction with the drive system of rotorcraft
101.
Sensor system 201 can be one of a variety of sensor systems capable of
measuring
torque in drive shaft. In one embodiment, sensor system 201 is a variable
reluctance sensor system comprising a combination of magnetic members and coil
members, for example. Other embodiments of sensor system 201 can include Hall
Effect sensors, optical sensors, to name a few.
Sensor system 201 can utilize a first hangar bearing 121 and a second hangar
bearing 123 as stationary sensor mounting platforms, while rotating sensor
components are adjacently located on tail rotor drive shaft 119. Tail rotor
drive shaft
119 can include a plurality of drive shaft segments, such as drive shaft
segment
119a. Preferably, sensor system 201 is associated with a drive shaft segment,
such
as segment 119a, that is a forwardly located drive shaft segment. Aftwardly
located
drive shaft segments tend to experience more positional variances due to the
deflections in tail member 109, which can cause undesired complexity or
errors.
Sensor system 201 can include a first sensor assembly 203 associated with a
forward portion of segment 119a, as well as a second sensor assembly 205
associated with an aft portion of segment 119a.
During operation, torque produced by engine 115 is transferred to tail rotor
blades
113 via tail rotor drive shaft 119. The torque load on tail rotor drive shaft
119 during
operation can cause a variable torsional deflection. The torsional deflection
can be
referred to as a "wind-up" or "phase shift", for example. Further, the
torsional
deflection can be the result of torsional loading in a variety of operational
conditions.
Sensor system 201 is configured to detect the difference in "phase shift"
between the
torsional deflections measured from first sensor assembly 203 and second
sensor
assembly 205. Sensor system 201 can include a temperature sensor to obtain
temperature data of tail rotor drive shaft 119. Measuring a temperature of
tail rotor
drive shaft 119 allows the processor to factor thermal expansion when
analyzing the
torsional phase shift of tail rotor drive shaft 119. A processor 207 is
configured to
process the measurement data from sensor system 201. In one embodiment,
processor 207 communicates the measurement data to a pilot of rotorcraft 101
in a
display 209. More specifically, display 209 can provide a visual indication of
real-
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time torque values, as well as past torque values, experienced in tail rotor
drive shaft
119.
System 201 can also include a health and usage monitoring system ("HUMS") 211.
Processor 207 can be configured to communicate measured torque data to HUMS
211 so that HUMS 211 can evaluate and provide useful health and usage data to
an
operator of rotorcraft 101. For example, if rotorcraft 101 were to experience
a
relatively high tail rotor drive shaft torque loading over a certain period of
time, then
HUMS 211 can communicate that information to an operator so that the operator
can
timely perform inspection and maintenance of bearings, as well as other
systems, in
accordance with the high torque loading, thus improving operational safety.
Conversely, if rotorcraft 101 were to experience a relatively low tail rotor
drive shaft
torque loading over a certain period of time, then HUMS 211 can communicate
that
information to an operator so that the operator can delay unnecessary
inspection
and maintenance of bearings, as well as other systems, in accordance with the
low
torque loading, thus saving expenses related to inspection and maintenance.
Further, HUMS 211 can be configured to store and communicate a torque history,
such as an over-torque history that may credit or debit a life span of the
tail rotor
drive shaft 119, and related components. Further, HUMS 211 can be configured
to
recognize and alert an operator to vibratory or deflection anomalies that may
reflect
a malfunctioning bearing or other drive system related component.
Referring briefly to Figure 4, a method 401 of optimizing a tail rotor drive
shaft is
schematically depicted. Method 401 allows a tail rotor drive shaft to be
optimally
sized so that certain rotorcraft operators can realize a benefit for
conservative
operations. Conventionally, a rotorcraft component, such as a tail rotor drive
shaft
was designed to survive a predetermined fatigue life, typically in terms of
hours
used. As such, the tail rotor drive shaft was designed to survive the life
usage of the
most abusive operator. An example of an abusive operator can be a tree hauler
that
puts a substantial amount and frequency of torque loading on the tail rotor
drive shaft
during usage of the rotorcraft by hauling logs. An operator that used the tail
rotor
drive shaft in a conservative manner was essentially penalized by having a
tail rotor
drive shaft that was heavier than necessary. Further, the conservative
operator had
to replace the tail rotor drive shaft when the predetermined life of the tail
rotor drive
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shaft had expired, even though the tail rotor drive shaft was still usable
since it had
been conservatively used. Further, the conservative operator was penalized by
having the requirement for inspection requirements that were more frequent
than
necessary.
Method 401 includes a step 403 of configuring a tail rotor drive shaft based
upon a
defined life usage. In one
example embodiment, the defined life usage is
approximately a median operator usage amount; however, the defined life usage
can
be any defined usage amount. In one embodiment, the defined life usage is
based
upon an accumulation of the amount of fatigue inducing torque cycles
experienced
by the tail rotor drive shaft during a plurality of operations. Preferably,
the defined
life usage is measurably less than what an abusive operator would place on the
tail
rotor drive shaft. Therefore, step 403 includes configuring tail rotor drive
shaft 119
with a more efficient (lighter weight) design since the defined life usage is
less than a
conventional life usage based an abusive rotorcraft operator.
Method 405 includes a step 405 of measuring actual usage of the tail rotor
drive
shaft. Sensor system 201 and HUMS 211, described further herein, are
particularly
well suited for implementing step 405 of method 401. For example, HUMS 211 can
store and communicate torque history of the tail rotor drive shaft, as well
any other
data that may be relevant to the evaluation of the health and life of the tail
rotor drive
shaft.
Method 405 further includes a step 407 of crediting and/or debiting a life of
the tail
rotor drive shaft based upon the measured data in step 405. A conservative
operator of rotorcraft 101 can derive usage credits that reduce inspection
intervals
and increase the replacement life span of the tail rotor drive shaft.
Similarly, an
abusive operator of rotorcraft 101 can derive usage debits that increase
inspection
intervals and decrease the replacement life span of the tail rotor drive
shaft. In one
embodiment, step 407 can be implemented throughout the life of the rotorcraft.
For
example, steps 405 and 407 can be implemented in real time. In another
embodiment, step 407 is implemented at an interval, such as once a week.
Further,
it should be appreciated that an operator can receive a usage credit for a
period of
conservative usage, then later receive a usage debit for a period of abusive
usage,
for example.
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One benefit of method 401 is that the tail rotor drive shaft, such as tail
rotor drive
shaft 119, can be more efficiently designed, therefore allowing a user realize
better
performance of rotorcraft 101. Further, method 401 encourages and rewards
conservative use the tail rotor drive shaft during operation of rotorcraft
101.
Referring now to Figure 3, an embodiment of a main rotor mast torque measuring
system 301 is illustrated. It is desirable to measure and monitor torque
loading in
main rotor mast 117; however, certain physical implementations of main rotor
mast
117 can make the variable torsional deflection experienced in main rotor mast
117
difficult and complicated to directly measure. For example, a main rotor mast
117
having a substantially high torsional stiffness will typically exhibit a
relatively low
torsional deflection for a given torque load. As such, directly measuring the
torsional
deflection, such as a "wind-up" or "phase shift" deflection, can be inaccurate
without
using expensive and highly calibrated instrumentation. Therefore, main rotor
mast
torque measuring system 301 utilizes a tail rotor drive shaft sensor system
201
(further discussed herein with regard to Figure 2) to derive a torque in main
rotor
mast 117.
Main rotor mast torque measuring system 301 can include a total engine torque
output sensor 303 in communication with a processor 305. Processor 305 is
configured to analyze data from total engine torque output sensor 303 and tail
rotor
drive shaft sensor system 201 to derive the torque in main rotor mast 117. In
one
embodiment, processor 305 uses the tail rotor drive shaft torque measurement
obtained by system 201 and the total output torque measured by output sensor
303
to derive the torque in main rotor mast 117 by using conservation of
energy/power.
It should be appreciated that total engine torque output sensor 303 can be the
sum
of torque from a plurality of engines. A health and usage monitoring system
("HUMS") 309 is configured similar to HUMS 211, except having additional
functionality for evaluating and providing useful health and usage data
pertaining to
torque in main rotor mast 117 to an operator of rotorcraft 101. Further, a
display 307
is configured similar to display 209 such that processor 305 can communicate
torque
data to a pilot of rotorcraft 101 in a display 209. More specifically, display
307 can
provide a visual indication of real-time torque values, as well as past torque
values,
experienced in main rotor mast 117 and/or tail rotor drive shaft 119.
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Processor 305 can be configured to consider any power consumed by an auxiliary
gearbox, or other power consuming system, when employing conservation of
energy/power principles to derive the torque in main rotor mast 117. Further,
processor 305 can be configured to consider other mechanical losses that may
be
necessary to derive an accurate torque value in main rotor mast 117.
Main rotor mast torque measuring system 301 can be particularly desirable in
conjunction with a main rotor mast 117 that has a high torsional stiffness, as
well as
in other situations. For example, it can be particularly desirable in some
aircraft
implementations to specifically monitor torque in tail rotor drive shaft 119
so as to
acquire data that is relevant to the health of the tail rotor drive system.
Thus, system
301 allows the torque in main rotor mast 117 to be derived without adding an
independent main rotor mast torque measuring sensor system.
Further, calculating main rotor mast torque by measuring tail rotor drive
shaft torque
can result in a more accurate reading of both main rotor mast torque and tail
rotor
drive shaft torque, as compared to calculating tail rotor drive shaft torque
from a
main rotor mast torque measurement. Most of the engine power is transferred to
the
main rotor mast. By way of illustration, approximately 80% of the engine power
can
be transferred to the main rotor mast, while the other 20% of the engine power
can
be transferred to the tail rotor drive shaft, not accounting for auxiliary
power
consuming systems. As such, if the tail rotor drive shaft torque were to be
calculated
from a main rotor mast torque measurement, then even a small amount of error
(such as 5% error) in the main rotor mast torque measurement is magnified when
the tail rotor drive shaft torque is derived therefrom. Therefore, it can be
more
accurate to measure the tail rotor drive shaft torque, and then calculate the
main
rotor mast torque therefrom.
Referring now also to Figure 5, a computer system 501 is schematically
illustrated.
Computer system 501 is configured for performing one or more functions with
regard
to the operation of methods and systems disclosed herein. Further, any
processing
and analysis can be partly or fully performed by computer system 501. Computer
system 501 can be partly or fully integrated with other aircraft computer
systems.
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The system 501 can include an input/output (I/O) interface 503, an analysis
engine
505, and a database 507. Alternative embodiments can combine or distribute the
input/output (I/O) interface 503, analysis engine 505, and database 507, as
desired.
Embodiments of the system 501 can include one or more computers that include
one
or more processors and memories configured for performing tasks described
herein.
This can include, for example, a computer having a central processing unit
(CPU)
and non-volatile memory that stores software instructions for instructing the
CPU to
perform at least some of the tasks described herein. This can also include,
for
example, two or more computers that are in communication via a computer
network,
where one or more of the computers include a CPU and non-volatile memory, and
one or more of the computer's non-volatile memory stores software instructions
for
instructing any of the CPU(s) to perform any of the tasks described herein.
Thus,
while the exemplary embodiment is described in terms of a discrete machine, it
should be appreciated that this description is non-limiting, and that the
present
description applies equally to numerous other arrangements involving one or
more
machines performing tasks distributed in any way among the one or more
machines.
It should also be appreciated that such machines need not be dedicated to
performing tasks described herein, but instead can be multi-purpose machines,
for
example computer workstations, that are suitable for also performing other
tasks.
The I/O interface 503 can provide a communication link between external users,
systems, and data sources and components of the system 501. The I/O interface
503 can be configured for allowing one or more users to input information to
the
system 501 via any known input device. Examples can include a keyboard, mouse,
touch screen, and/or any other desired input device. The I/O interface 503 can
be
configured for allowing one or more users to receive information output from
the
system 501 via any known output device. Examples can include a display
monitor, a
printer, cockpit display, and/or any other desired output device. The I/O
interface
503 can be configured for allowing other systems to communicate with the
system
501. For example, the I/O interface 503 can allow one or more remote
computer(s)
to access information, input information, and/or remotely instruct the system
501 to
perform one or more of the tasks described herein. The I/O interface 503 can
be
configured for allowing communication with one or more remote data sources.
For
example, the I/O interface 503 can allow one or more remote data source(s) to
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access information, input information, and/or remotely instruct the system 501
to
perform one or more of the tasks described herein.
The database 507 provides persistent data storage for system 501. While the
term
"database" is primarily used, a memory or other suitable data storage
arrangement
may provide the functionality of the database 507. In alternative embodiments,
the
database 507 can be integral to or separate from the system 501 and can
operate on
one or more computers. The database 507 preferably provides non-volatile data
storage for any information suitable to support the operation of system 201,
system
301, and method 401, including various types of data discussed further herein.
The
analysis engine 505 can include various combinations of one or more
processors,
memories, and software components.
The sensor system of the present application provides significant advantages,
including: 1) enabling the derivation of a torque measurement in a tail rotor
drive
shaft; 2) providing a system for determining a main rotor mast torque value
without
directly measuring main rotor mast torque; 3) providing a system for
determining a
main rotor mast torque value where the rotor mast torsional stiffness makes
direct
measurement of main rotor mast torque undesirable; 4) providing a system for
using
main rotor mast torque and tail rotor drive shaft torque in a health and usage
monitoring system; 5) providing a method of optimizing a tail rotor drive
shaft; and 6)
providing a method of encouraging and rewarding conservative use of tail rotor
drive
shaft during operation of the rotorcraft.
The particular embodiments disclosed herein are illustrative only, as the
system and
method may be modified and practiced in different but equivalent manners
apparent
to those skilled in the art having the benefit of the teachings herein.
Modifications,
additions, or omissions may be made to the system described herein without
departing from the scope of the invention. The components of the system may be
integrated or separated. Moreover, the operations of the system may be
performed
by more, fewer, or other components.
Furthermore, no limitations are intended to the details of construction or
design
herein shown, other than as described in the claims below. It is therefore
evident
that the particular embodiments disclosed above may be altered or modified and
all
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such variations are considered within the scope of the disclosure.
Accordingly, the
protection sought herein is as set forth in the claims below.
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